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Transmission Hard 1-2 Shift


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#1 cmoore74

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Posted 08 November 2006 - 01:07 PM

I had a very hard 1-2 shift last night for the first time ever. I towed my boat back home from the ramp (about 1 hour of driving), shut off the truck, and unhooked the boat. About an hour later I hopped in the truck, pulled out of the driveway and experienced a very hard shift from 1st to 2nd. It hasn't done it since.

My question is to those that have had this problem with hard 1-2 shifting, is it intermittent or does it happen every shift? If it is intermittent, does it become more frequent over time?

The truck only has about 6k miles on it so it's under warranty. I have to bring it in anyhow because the power to the rearview mirror was coming on and off in a very heavy rainstorm a few weeks ago and I'll ask them to take a look, but you know what happens when the dealership can't reproduce the problem, they do nothing.

Also was wondering if this is a sign that I will have future transmission issues. If so, I may opt for that extended warranty after all.
Chris
2006 GMC Sierra 1500 Crew Cab 5.3L 4x4 Z71 Dark Green Metallic
Performance Mods: Superchips Flashpaq, AEM Brute Force intake, Corsa Touring exhaust
Functional Mods: Line-X spray-in bed liner, BakFlip hard folding tonneau cover, Nasta stainless steel step bars, AVS window vents and bug deflector, Cover-Craft seat covers, Husky mudguards, Scan Gauge 2 w/ x-gauge, DU-HA behind rear seat storage bin

#2 cmoore74

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Posted 09 November 2006 - 09:33 AM

A search showed the hard 1-2 shift is fairly common. Must be someone out there that can help.

Anyone?
Chris
2006 GMC Sierra 1500 Crew Cab 5.3L 4x4 Z71 Dark Green Metallic
Performance Mods: Superchips Flashpaq, AEM Brute Force intake, Corsa Touring exhaust
Functional Mods: Line-X spray-in bed liner, BakFlip hard folding tonneau cover, Nasta stainless steel step bars, AVS window vents and bug deflector, Cover-Craft seat covers, Husky mudguards, Scan Gauge 2 w/ x-gauge, DU-HA behind rear seat storage bin

#3 Bish

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Posted 09 November 2006 - 12:33 PM

A search showed the hard 1-2 shift is fairly common. Must be someone out there that can help.

Anyone?

<{POST_SNAPBACK}>


A hard 1-2 shift occurs when the trans goes into limp mode. I had a TPS sensor go bad and the trans started shifting really hard to the point I thought I had a problem with the trans. Replacing the TPS and it went away.

I believe when the computer senses any problem, it boosts line pressure in the trans so as to get you home in case something is slipping. The end effect is the hard shift. I believe many different trouble codes can put the trans in limp mode. If the code goes away on it's own, the trans should shift normally. I bet if you scan your vehicle, you will see something in the history. Could have been the trans overheating during your tow too.

Edited by Bish, 09 November 2006 - 12:34 PM.

2008 Yukon Denali AWD Red Jewel
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#4 cmoore74

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Posted 09 November 2006 - 03:01 PM

A search showed the hard 1-2 shift is fairly common. Must be someone out there that can help.

Anyone?

<{POST_SNAPBACK}>


A hard 1-2 shift occurs when the trans goes into limp mode. I had a TPS sensor go bad and the trans started shifting really hard to the point I thought I had a problem with the trans. Replacing the TPS and it went away.

I believe when the computer senses any problem, it boosts line pressure in the trans so as to get you home in case something is slipping. The end effect is the hard shift. I believe many different trouble codes can put the trans in limp mode. If the code goes away on it's own, the trans should shift normally. I bet if you scan your vehicle, you will see something in the history. Could have been the trans overheating during your tow too.

<{POST_SNAPBACK}>


I should hope it's not the transmission over-heating. It's not like it's scorching hot outside (it was only about 50 deg F) and the total weight of boat, trailer, gas, gear, etc. is around 3500 lbs. whereas the tow rating is 7400 lbs.

I never overheated the transmission on my little S-10 with the 4.3L V6 towing this boat and I've towed on days where it was close to 100 deg outside.

Just the same I'll take a whiff of the tranny fluid when I get home tonight.

If I had a code wouldn't the Service Engine light come on or does that only happen if the code is frequent?
Chris
2006 GMC Sierra 1500 Crew Cab 5.3L 4x4 Z71 Dark Green Metallic
Performance Mods: Superchips Flashpaq, AEM Brute Force intake, Corsa Touring exhaust
Functional Mods: Line-X spray-in bed liner, BakFlip hard folding tonneau cover, Nasta stainless steel step bars, AVS window vents and bug deflector, Cover-Craft seat covers, Husky mudguards, Scan Gauge 2 w/ x-gauge, DU-HA behind rear seat storage bin

#5 Bish

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Posted 09 November 2006 - 05:26 PM

A search showed the hard 1-2 shift is fairly common. Must be someone out there that can help.

Anyone?

<{POST_SNAPBACK}>


A hard 1-2 shift occurs when the trans goes into limp mode. I had a TPS sensor go bad and the trans started shifting really hard to the point I thought I had a problem with the trans. Replacing the TPS and it went away.

I believe when the computer senses any problem, it boosts line pressure in the trans so as to get you home in case something is slipping. The end effect is the hard shift. I believe many different trouble codes can put the trans in limp mode. If the code goes away on it's own, the trans should shift normally. I bet if you scan your vehicle, you will see something in the history. Could have been the trans overheating during your tow too.

<{POST_SNAPBACK}>


I should hope it's not the transmission over-heating. It's not like it's scorching hot outside (it was only about 50 deg F) and the total weight of boat, trailer, gas, gear, etc. is around 3500 lbs. whereas the tow rating is 7400 lbs.

I never overheated the transmission on my little S-10 with the 4.3L V6 towing this boat and I've towed on days where it was close to 100 deg outside.

Just the same I'll take a whiff of the tranny fluid when I get home tonight.

If I had a code wouldn't the Service Engine light come on or does that only happen if the code is frequent?

<{POST_SNAPBACK}>


My understanding is some codes set the light and some don't but then again, I'm no expert. Also, I have found it can be very easy to overheat the trans in certain situations. When I first towed with my Tahoe, I towed in OD and when the trans is hunting gears or locking/unlocking the converter, it can heat up quickly. I'm not saying your's is overheating but it is possible even on a cool day. Got a tranny cooler? A quick sniff of the fluid should confirm/deny an overheat problem.
2008 Yukon Denali AWD Red Jewel
6.2L, 6L80E EFILive and a BlackBearPerformance tune. GMPP CAI, Hotchkis Front/Rear Sway Bars
2008 Buick Enclave - All GM for us now!

#6 Pureiron

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Posted 09 November 2006 - 05:40 PM

This is good info folks, thanks.... Seems my tranny overheated.

#7 cmoore74

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Posted 09 November 2006 - 08:27 PM

I always tow in drive and it has the tow package which has the factory transmission cooler.

I took a look at the fluid, it's fine. It's red and smells new as it should with just under 6000 miles on it. The cause is definitely not an over-heated transmission.
Chris
2006 GMC Sierra 1500 Crew Cab 5.3L 4x4 Z71 Dark Green Metallic
Performance Mods: Superchips Flashpaq, AEM Brute Force intake, Corsa Touring exhaust
Functional Mods: Line-X spray-in bed liner, BakFlip hard folding tonneau cover, Nasta stainless steel step bars, AVS window vents and bug deflector, Cover-Craft seat covers, Husky mudguards, Scan Gauge 2 w/ x-gauge, DU-HA behind rear seat storage bin

#8 cmoore74

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Posted 10 November 2006 - 12:23 PM

Anyone out there that had the hard 1-2 shift and then a failed transmission?

What was the chain of events (i.e. how long from hard 1-2 shifts to failure, did the 1-2 hard shifting become more frequent or more severe, etc.)?

Is the hard 1-2 shift really even an indicator that the transmission is destined to fail early?
Chris
2006 GMC Sierra 1500 Crew Cab 5.3L 4x4 Z71 Dark Green Metallic
Performance Mods: Superchips Flashpaq, AEM Brute Force intake, Corsa Touring exhaust
Functional Mods: Line-X spray-in bed liner, BakFlip hard folding tonneau cover, Nasta stainless steel step bars, AVS window vents and bug deflector, Cover-Craft seat covers, Husky mudguards, Scan Gauge 2 w/ x-gauge, DU-HA behind rear seat storage bin

#9 cmoore74

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Posted 12 November 2006 - 11:30 AM

Anyone out there that had the hard 1-2 shift and then a failed transmission?

What was the chain of events (i.e. how long from hard 1-2 shifts to failure, did the 1-2 hard shifting become more frequent or more severe, etc.)?

Is the hard 1-2 shift really even an indicator that the transmission is destined to fail early?

<{POST_SNAPBACK}>


Anyone?

Maybe I'm worrying over nothing...
Chris
2006 GMC Sierra 1500 Crew Cab 5.3L 4x4 Z71 Dark Green Metallic
Performance Mods: Superchips Flashpaq, AEM Brute Force intake, Corsa Touring exhaust
Functional Mods: Line-X spray-in bed liner, BakFlip hard folding tonneau cover, Nasta stainless steel step bars, AVS window vents and bug deflector, Cover-Craft seat covers, Husky mudguards, Scan Gauge 2 w/ x-gauge, DU-HA behind rear seat storage bin